It is known to be able to zoom in on a portion of an image captured using a digital camera or videocamera. For example, digital cameras commonly include a screen upon which an image can be previewed before capture, and viewed post-capture. The screen can be used to manually zoom into and view portions of a captured image at preset magnification factors for example.
Some devices provide a semi-automatic zoom function. Generally, such systems automatically zoom into a captured image by a predetermined amount following image capture. A user may initiate such a function by pressing a button on the device following capture of an image, and a magnified portion of the captured image is then displayed. For example, a central portion of the image may be displayed at increased magnification since, in such systems, this is generally taken to be the area in which salient material in the image is located.
Techniques exist for determining an area of potential saliency in an image, and these have been applied to systems in order to effect automatic cropping of the image. For example, U.S. Pat. No. 6,654,507 describes a method for cropping a portion of an image by identifying a potential main subject of the image. A belief map is generated comprising image features, each feature having a measure assigned thereto representative of the probability that it is the main subject of the image. The image is cropped to include the feature with the highest probability.
Further techniques exist for providing automatic cropping of an image in response to a determination of salient portions in the image. For example, European Patent Application No. 02251070.5.
In, Yu-Fei Ma, Hong-Jiang Zhang, “Contrast-based image attention analysis by using fuzzy growing,” Proceedings of the eleventh ACM international conference on Multimedia, November 2003, a saliency map is created using normalized local contrast measures. Salient regions are identified using a region growing method.
In Xian-Sheng Hua, Lie Lu, Hong-Jiang Zhang, “Automatically converting photographic series into video,” Proceedings of the 12th annual ACM international conference on Multimedia, October 2004, saliency locations areas found using Yu-Fei Ma, Hong-Jiang Zhang, “Contrast-based image attention analysis by using fuzzy growing,” Proceedings of the eleventh ACM international conference on Multimedia, November 2003, are used to generate a dynamic viewing path. The method designates saliency locations as keyframes and then uses explicit film making rules to place them in a preferred order.
Also in this connection, WO GB01/05683 provides a system for determining salient portions in an image and generating an automatic rostrum path for the image in order that salient portions can be displayed along the path.